The present disclosure relates to image processing apparatuses and methods, and more particularly, to an image processing apparatus and method that can reduce the amount of encoded image data more easily.
Pathological diagnosis using a digital pathology imaging (DPI) system has been applied to biopsies (tissue diagnosis) and is now finding wide application in cytological diagnosis as well as biopsies.
A biopsy is a medical test for an examination or operation conducted as follows. A diseased sample is collected by being cut out with a knife and is sliced into thin portions. The sliced portions are then stained and are examined under a microscope. Generally, in a biopsy, cells are examined as a cell group, and are checked for abnormalities in terms of the size, shape, and arrangement of the cells in the cell group. Examinations are also made for the presence of abnormal cells in the cell group.
In contrast, cytological diagnosis is a medical test conducted as follows. Naturally exfoliated cells (sputum cytology), intentionally exfoliated cells (exfoliative cytology), or cells aspirated through a needle (aspiration cytology) are stained, and are examined under a microscope. Generally, in cytological diagnosis, a small number of cells are examined, and are checked for abnormalities in terms of the size, shape, etc., of each cell or the nucleus thereof.
In the DPI system, images of such tissues or cells (images obtained by imaging the tissues or cells under a microscope) are handled as digital data. Accordingly, various types of image processing may be performed on such images (digital data) in accordance with the purpose of use.
Generally, such digital data is encoded by using an encoding method, such as Joint Photographic Experts Group (JPEG), and the amount of data is reduced.
The amount of JPEG encoded data may be further reduced by performing conversion processing (transcoding) on the encoded data. Japanese Patent Nos. 3856292, 3948024, and 3948025 disclose methods for further reducing the amount of encoded data using transcoding.
In the methods disclosed in the above patents, the amount of data is reduced by transforming Discrete Cosine Transform (DCT) coefficients. Such data reduction using transcoding can be used for all JPEG encoded data.
In the methods disclosed in the above patents, however, consideration is not given to the characteristics of images (digital data) obtained by imaging tissues or cells in cytological diagnosis, which may make it difficult to sufficiently reduce the amount of data.
In the DPI system, specimens are placed on a transparent plate and are imaged with a microscope. Because of this reason, generally, cytopathic digital images or histopathlogic digital images handled in the DPI system include many blank portions (regions) without the presence of cells. Particularly, digital images captured in cytological diagnosis include many blank portions without the presence of cells because the number of cells examined is small. Such blank portions are not used for examination, but the image data of the cells is compressed with noise included in such blank portions. That is, the blank portions also count toward the amount of data, and the amount of data is increased because of such unnecessary blank portions.
It is thus expected that the amount of data will further be reduced by performing transcoding by taking such characteristics into consideration. In the related art, however, no methods for performing such transcoding have been proposed, and it is difficult to reduce the amount of data sufficiently.
It is thus desirable to reduce the amount of encoded image data more easily.